Existing commercial approaches for delivering volatile antimicrobial oils into a headspace (such as in shoe-boxes) typically involve an absorbent pad, tissue or film which is charged with the volatile oil (by soaking it or exposing it to an atmosphere of the volatile oil) and stored in air-tight packaging before use. One major disadvantage with this approach is that as soon as the pad/tissue/film is removed from its air-tight packaging, as there is little control over the release rate, it may lose a large amount/all of the volatile oil before the release of the volatile oil into the headspace is desired. For example, to use in a supply chain for packaging freshly harvested berries, the material after removal from air-tight packaging, may be exposed to ambient conditions, followed by forced air cooling for several hours, during which time no appreciable release of volatile oil is desired.
Alternative approaches may involve casting coatings from solvents which contain the dissolved volatile oil and a hydrophobic binder. One major disadvantage with this approach is that most of the volatile oil typically escapes from the coating during the drying process, and during storage.
Additional approaches involve the use of beta-cyclodextrin (beta-CD) to encapsulate the volatile oil within a coating. One major disadvantage with beta-CD is its poor solubility in common casting solvents (including water), and its high molecular weight (Mw=1135) relative to the molecular weight of a typical volatile oil. Due to its high molecular weight, a relatively large mass of beta-CD needs to be used to encapsulate the volatile oil, resulting in high expense and relatively low levels of volatile oil incorporated into the coating.
Thus, there remains a need to develop effective material with controlled release of volatile compounds, in particular for agricultural applications.